This invention relates to a process for curing a radiation curable coating media.
Curing reactions by radiation are mainly conducted by radical polymerization, so that there takes place an oxygen inhibition of the reaction on exposure to air. In order to avoid such a trouble, it is general to conduct the curing reaction under an inert gas atmosphere. But this process has the following disadvantages:
(1) Since a large amount of an inert gas is required, the cost of equipment and operating cost become higher. PA0 (2) Since the oxygen concentration changes with an influence of coating speed, it is difficult to control curing properties at a constant level.
In order to improve such disadvantages, it is proposed a process wherein oxygen is excluded by laminating a overlapped material which has been prepared otherwise on a coating media (hereinafter referred to as "the laminating process"). The laminating process has advantages over the above-mentioned process in that the inert gas is not required, and the control of cured properties is easy due to no change in the oxygen concentration caused by coating speed. But the laminating process has the following problems:
(1) It is necessary to prepare various sizes of overlapped materials.
(2) Since the overlapped materials are deteriorated by radiation, there is a limit for re-use. Thus, the overlapped materials should be exchanged in a certain period.
(3) Since special unwinding equipment and winding equipment for the overlapped material are necessary, the cost of equipment becomes higher and a place for such equipments is also required.